Field
Various features pertain to active depth sensing and more specifically to techniques to compensate for different reflectivity/absorption coefficients of objects in a scene when performing active depth sensing system using structured light.
Background
In active sensing, a known pattern (e.g., code mask) is used to illuminate a scene or object in process often referred to as “structured light”. The structure of the pattern projected on the scene or object encodes depth information for the scene or object. Once the pattern is found in a received image, the 3-dimensional scene or object may be reconstructed. The relationship between the known projected pattern and the decoded one can be used to derive depth information on the captured scene.
A receiver/camera sensor may capture an image of a scene from the incident light coming from a reflection of a light source onto the scene (e.g., person, object, location, etc.). The intensity of the incident light may depend on: (a) the reflectance properties of the surfaces in the scene, (b) the power of the light that generates the projected pattern, and/or (c) ambient light. If the incident light on the camera sensor is too strong, it saturates the sensor. If it is too weak, the camera sensor does not capture the variations in reflectivity of the scene. Even within a scene, depending on the type of surfaces being captured in an image, both situations (e.g., captured light too strong and too weak) can happen at the same time. If no adjustment to the strength of incident light is included in the system, it's impossible to capture the variations in illumination of the projected pattern (e.g., code mask) for a wide range of situations (different ambient lights, different pre-set power of the light source, different surface types).
Consequently, a solution is needed to compensate for variations in incident light intensity when performing depth sensing of a scene using a structured light system.